The present invention relates to an object detection apparatus, a distance measuring apparatus, and an object detection method.
An object detection method is known in which an object is detected by radiating a wave such as a radio wave, an ultrasonic wave or light to an object and detecting a reflected wave from the object. The time period from the moment at which the wave is radiated to the moment at which the reflected wave is detected is measured to enable computation of the distance from the wave radiation position to the object. This method, however, cannot be used with respect to an object having a wave absorbing property.
Japanese Laid-Open Patent Publication No. 2003-196664 discloses an object detection apparatus which detects an object on the basis of an image picked up by an image pickup device such as a CCD camera. This object detection apparatus obtains two or more images picked up successively with respect to time and computes optical flows from the obtained images. The object detection apparatus separates each image into a region predicted to include the object and a region predicted to include no object portion. The object detection apparatus executes predetermined processing, e.g., pattern matching on the predicted object-including region to detect the object from the region. This kind of object detection apparatus is capable of detecting an object without being influenced by the properties of the object, e.g., the property of easily absorbing waves. After the detection of the object, the distance to the object can be obtained on the basis of the principle of triangulation for example.
The object detection apparatus disclosed in Japanese Laid-Open Patent Publication No. 2003-196664 requires complicated computation processing for separating a region including an object and a region including no object portion from an obtained image. In this computation processing, if the object has a shadow, there is a possibility of the shadow being erroneously recognized as a portion of the object. For this reason, the object detection apparatus cannot detect the object with accuracy. As a result, the distance to the object cannot be computed with accuracy.